Conventionally, a game such as an action game or a role-playing game proceeds in such a manner that a player character is caused to act within a virtual game space in response to a user's manipulation. In this kind of game, plural game devices can be connected to each other via communication lines and plural users can cooperate with each other to fight with an enemy character. See e.g., Monster Hunter Portable 2ndG Official Guidebook,” Enterbrain, Inc., Aug. 1, 2008, p. 34-35 (hereinafter “Monster Hunter”). In the game of Monster Hunter, player characters manipulated by multiple players cooperate with each other to fight an enemy character that appears in the virtual game space. In this fight, each player character makes an attack corresponding to its ability on the enemy character. The enemy character reduces its vitality according to damage to the enemy character. At a time point when the vitality reaches zero, the enemy character is beaten.